One of such upgrading processes is the dewaxing of hydrocarbon feedstocks, such as gasoils. In GB-A No. 2,141,733, a process is described in which a hydrocarbonaceous feedstock is contacted with a shape selective catalyst in the presence of hydrogen at elevated temperature and pressure to reduce the pour point of the feedstock. In the process n-paraffins are selectively cracked thereby reducing the pour point To increase the pour point reduction ammonia and hydrogen sulphide are added to the reaction zone. The temperatures are from 232.degree. to 538.degree. C., the pressures are from about 8 to 208 bar, usually about 40 bar, and the liquid hourly space velocity will generally be between 0.1 to 10 h.sup.-1.
The drawbacks of this process reside in the relatively high pressure that is to be applied and the required presence of hydrogen. Moreover it appeared that besides the desired product, i.e. dewaxed gas oil, saturated gaseous products (C.sub.2-4) were obtained that have intrinsically low economic value.
In U.S. Pat No. 4,171,257 a process is described in which a hydrocarbonaceous feedstock is upgraded by contacting the feedstock with a ZSM-5 containing catalyst at a pressure below 14 bar, a temperature of 260.degree. to 427.degree. C. and a space velocity of 0.1 to 15 l/l.h. The feedstock must contain less than 5 ppmw of nitrogen-containing compounds, calculated as nitrogen. The products include olefinic hydrocarbons, such as propene and butenes.
The latter known process has as drawback that the feedstock must have been severely denitrified. This is necesserary as the more nitrogenous feedstocks would deactivate the catalyst rapidly.